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Abstract-L-arginine is the substrate used by NO synthase to produce the vasodilator NO. However, in several human diseases, such as hyperhomocysteinemia, diabetes mellitus, and hypertension, there is an increase in serum levels of methylated L-arginines, such as asymmetrical dimethylarginine (ADMA), which cannot be used by NO synthase to produce NO. Yet, the functional consequence of increased levels of ADMA on the vasomotor function of resistance vessels has not been delineated. We hypothesized that elevated levels of exogenous ADMA inhibit NO mediation of flow/shear stress-dependent dilation of isolated arterioles. In the presence of indomethacin, isolated arterioles from rat gracilis muscle (Ϸ165 m at 80 mm Hg) were incubated with ADMA (10 Ϫ4 mol/L), which eliminated the dilations to increases in intraluminal flow (control: from 164Ϯ5.4 to 188Ϯ3.8 m versus ADMA: from 171Ϯ6.1 to 173Ϯ6.3 m at 20 L/min). ADMA did not affect dilations to nifedipine (10 Ϫ6 mol/L; control: 63.4Ϯ2%, ADMA: 65.8Ϯ3%) or 8-bromo cGMP (10 Ϫ4 mol/L; control: 51.2Ϯ2.1%, ADMA: 49.3Ϯ3.4%). In addition, ADMA elicited significant constriction of arterioles (from 173Ϯ17 m to 138Ϯ16 m at 80 mm Hg), which was prevented by previous incubation of arterioles with polyethylene-glycol (PEG) superoxide dismutase (SOD; 120 U/mL, control: 155Ϯ11 m versus ADMA: 150Ϯ14 m). Correspondingly, ADMA increased PEG-SOD reversible manner the production of vascular superoxide assessed by lucigenin-enhanced chemiluminescence and ethidium bromide fluorescence. Thus, increased levels of ADMA in various diseases could inhibit the regulation of arteriolar resistance by shear stress-induced release of NO and elicit superoxide-mediated increase in basal tone, both of which favor the development of hypertension. Key Words: ADMA Ⅲ flow-dependent dilation Ⅲ superoxide Ⅲ nitric oxide Ⅲ arteriolar tone T he production of the important signaling molecule NO is regulated and modulated by several physiological and pathological mechanisms. 1 It has been well established that L-arginine is the physiological substrate of NO synthase (NOS) to produce the vasodilator substance NO. 1 Supporting this conclusion, we have found previously that exogenous L-arginine increases the synthesis of NO and augments NO-mediated arteriolar vasodilation. 2 In 1992, Vallance et al 3 described that Ͼ10 mg of methylated L-arginines, such as asymmetrical dimethylarginine (ADMA), is excreted in urine in 24 hours indicating that these forms of L-arginine exist in vivo. Further studies revealed that in several human diseases, such as hyperhomocysteinemia, 4 diabetes mellitus, 5 hypertension, 6 coronary artery disease, 7 peripheral arterial occlusive disease, 8 and pulmonary hypertension, 9 and as result of smoking, 10 there is an increase in the serum level of methylated L-arginines, such as ADMA. The pathological importance of these findings is underscored by the biochemical mechanism showing that NOS cannot use ADMA to produce NO. 3 Interestingly, a significant positive correlation between age and ADMA le...

Labinskyy N, Mukhopadhyay P, Toth J, Szalai G, Veres M, Losonczy G, Pinto JT, Pacher P, Ballabh P, Podlutsky A, Austad SN, Csiszar A, Ungvari Z. Longevity is associated with increased vascular resistance to high glucose-induced oxidative stress and inflammatory gene expression in Peromyscus leucopus. Am J Physiol Heart Circ Physiol 296: H946 -H956, 2009. First published January 30, 2009 doi:10.1152/ajpheart.00693.2008.-Vascular aging is characterized by increased oxidative stress and proinflammatory phenotypic alterations. Metabolic stress, such as hyperglycemia in diabetes, is known to increase the production of ROS and promote inflammatory gene expression, accelerating vascular aging. The oxidative stress hypothesis of aging predicts that vascular cells of long-lived species exhibit lower steady-state production of ROS and/or superior resistance to the prooxidant effects of metabolic stress. We tested this hypothesis using two taxonomically related rodents, the white-footed mouse (Peromyscus leucopus) and the house mouse (Mus musculus), which show a more than twofold difference in maximum lifespan potential (8.2 and 3.5 yr, respectively). We compared interspecies differences in steady-state and high glucose (HG; 30 mmol/l)-induced production of O 2•Ϫ and H2O2, endothelial function, mitochondrial ROS generation, and inflammatory gene expression in cultured aortic segments. In P. leucopus aortas, steady-state endothelial O 2•Ϫ and H2O2 production and ROS generation by mitochondria were less than in M. musculus vessels. Furthermore, vessels of P. leucopus were more resistant to the prooxidant effects of HG. Primary fibroblasts from P. leucopus also exhibited less steady-state and HG-induced ROS production than M. musculus cells. In M. musculus arteries, HG elicited significant upregulation of inflammatory markers (TNF-␣, IL-6, ICAM-1, VCAM, and monocyte chemoattractant protein-1). In contrast, the proinflammatory effects of HG were blunted in P. leucopus vessels. Thus, increased life span potential in P. leucopus is associated with decreased cellular ROS generation and increased resistance to prooxidant and proinflammatory effects of metabolic stress, which accord with predictions of the oxidative stress hypothesis of aging.senescence; comparative biology; vascular disease; atherosclerosis AGE IS A MAJOR RISK FACTOR for cardiovascular disease, which remains the leading cause of morbidity and mortality of older Americans. Despite recent advances in the biology of aging, the factors determining successful cardiovascular aging are still not completely understood (15, 53, 54). Mammalian life span ranges 100-fold, and comparative studies (53, 54) on longlived, successfully aging animals can elucidate key cellular mechanisms that may contribute importantly to successful cardiovascular aging. We initiated a series of studies to compare mechanisms related to oxidative stress, oxidative stress resistance, and redox signaling between long-living species and shorter-living ones to test predictions of the oxidative stress t...

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The population in the Western world is aging. In 1996 those aged 60 years and over formed 21% of the EU population, by 2022 this proportion will have risen to 27%. Based on current trends a third of the EU population could be 60 years of age and over by the age 2050. Epidemiological studies suggest that even in the absence of other risk factors (e.g. diabetes, hypertension, hypercholesterolemia), advanced age itself significantly increases cardiovascular morbidity by promoting the development of atherosclerosis and by impairing normal cellular functions. One of the most prominent organs affected by aging is the kidney. There is evidence that age-associated phenotypic changes may be an important cause of renal failure. We propose that vascular oxidative stress and inflammation are generalized phenomena during senescence, which importantly contribute to the morphological and functional changes in the aging kidney. The present review focuses on some of the mechanisms by which advanced age may promote vascular oxidative and nitrosative stress and the possible downstream mechanisms by which reactive oxygen and nitrogen species may impair vascular and renal function in aging.

Hyperglycemia increases glucose metabolism via the polyol pathway, which results in elevations of intracellular sorbitol concentration. Thus we hypothesized that elevated level of sorbitol contributes to the development of hyperglycemia-induced dysfunction of microvessels. In isolated, pressurized (80 mmHg) rat gracilis muscle arterioles (approximately 150 microm), high glucose treatment (25 mM) induced reduction in flow-dependent dilation (from maximum of 39 +/- 2% to 15 +/- 1%), which was significantly mitigated by an aldose reductase inhibitor, zopolrestat (maximum 27 +/- 2%). Increasing doses of sorbitol (10(-10)-10(-4) M) elicited dose-dependent constrictions (maximum 22 +/- 3%), which were abolished by endothelium removal, a prostaglandin H(2)/thromboxane A(2) (PGH(2)/TXA(2)) receptor (TP) antagonist SQ-29548, or superoxide dismutase (SOD) plus catalase (CAT). Incubation of arterioles with sorbitol (10(-7) M) reduced flow-dependent dilations (from maximum of 39 +/- 2% to 20 +/- 1.5%), which was not further affected by inhibition of nitric oxide synthase by N(omega)-nitro-l-arginine methyl ester but was prevented by SOD plus CAT and mitigated by SQ-29548. Nitric oxide donor sodium nitroprusside-induced (10(-9)-10(-6) M) dilations were also decreased in a SQ-29548 and SOD plus CAT-reversible manner, whereas adenosine dilations were not affected by sorbitol exposure. Sorbitol significantly increased arterial superoxide production detected by lucigenin-enhanced chemiluminescence, which was inhibited by SOD plus CAT. Sorbitol treatment also increased arterial formation of 3-nitrotyrosine. We suggest that hyperglycemia by elevating intracellular sorbitol induces oxidative stress, which interferes with nitric oxide bioavailability and promotes PGH(2)/TXA(2) release, both of which affect regulation of vasomotor responses of arterioles. Thus increased activity of the polyol pathway may contribute to the development of microvascular dysfunction in diabetes mellitus.

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Pharmacokinetic (PK) models simplify biological complexity by dividing the body into interconnected compartments. The time course of the chemical's amount (or concentration) in each compartment is then expressed as a system of ordinary differential equations. The complexity of the resulting system of equations can rapidly increase if a precise description of the organism is needed. However, difficulties arise when the PK model contains more variables and parameters than comfortable for mathematical and computational treatment. To overcome such difficulties, mathematical lumping methods are new and powerful tools. Such methods aim at reducing a differential system by aggregating several variables into one. Typically, the lumped model is still a differential equation system, whose variables are interpretable in terms of variables of the original system. In practice, the reduced model is usually required to satisfy some constraints. For example, it may be necessary to keep state variables of interest for prediction unlumped. To accommodate such constraints, constrained lumping methods have are also available. After presenting the theory, we study, here, through practical examples, the potential of such methods in toxico/pharmacokinetics. As a tutorial, we first simplify a 2-compartment pharmacokinetic model by symbolic lumping. We then explore the reduction of a 6-compartment physiologically based pharmacokinetic model for 1,3-butadiene with numerical constrained lumping. The lumping methods presented here can be easily automated, and are applicable to first-order ordinary differential equation systems.